1 - Copley-Fairlawn City Schools



You are designing a centrifuge to spin at a rate of 15,000 rev/min. (a) Calculate the maximum centripetal acceleration that a test-tube sample held in the centrifuge arm 15 cm from the rotation axis must withstand. (b) It takes 1 min, 15 s for the centrifuge to spin up to its maximum rate of revolution from rest. Calculate the magnitude of the tangential acceleration of the centrifuge while it is spinning up, assuming that the tangential acceleration is constant.

1. While trying out for the position of pitcher on your high school baseball team, you throw a fastball at 87 mi/h toward home plate, which is 18.4 m away. How far does the ball drop due to effects of gravity by the time it reaches home plate? (Ignore any effects due to air resistance.)

2. A cannonball is fired with initial speed v0 at an angle 30° above the horizontal from a height of 40 m above the ground. The projectile strikes the ground with a speed of 1.2v0. Find v0. (Ignore any effects due to air resistance.)

3. A cannon barrel is elevated 45° above the horizontal. It fires a ball with a speed of 300 m/s. (a) What height does the ball reach? (b) How long is the ball in the air? (c) What is the horizontal range of the cannon ball? (Ignore any effects due to air resistance.)

4. A projectile is fired into the air from the top of a 200-m cliff above a valley. Its initial velocity is 60 m/s at 60° above the horizontal. Where does the projectile land? (Ignore any effects due to air resistance.)

5. A football quarterback throws a pass at an angle of 36.5°. He releases the pass 3.50 m behind the line of scrimmage. His receiver left the line of scrimmage 2.50 s earlier, goes straight downfield at a constant speed of 7.50 m/s. In order that the pass land gently in the receiver's hands without the receiver breaking stride, with what speed must the quarterback throw the pass? Assume that the ball is released at the same height it is caught and that the receiver is straight downfield from the quarterback at the time of release. (Ignore any effects due to air resistance.)

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